Hi all
With some luck we can make this tread into 10-year anv
Sebastian, to answer your questions.
1. In short no. I have just been "killing" Das-Modul and other PCB's testing out my topology. The last test turned out quite well, so I am rather sure of the concept.
The PCB will be around 14 x 4 cm (=5,5 x 1,57 inches), double sided. The 4 x LM3886 will be along the (long side).
Each of the LM3886 will receiver the same signal and then joint in parallel at the output, so we are taking about 4 x LM3886 in parallel.
(I am thinking about the option of "2x2", so one PCB could be used as a stereo-amp, each channel being 2 x LM3886 in parallel).
Ther will be no adjustments and I have made an effort to use standard components.
2. Yes
You are right about the DC-servo, I just wanted to try something more simpel with almost the same performance. If it can make more people try out the LM3886 in different configurations, my mission is completed
Have fun
Thomas
Dear Thomas,
Thank your for your answers. Even though I studied a lot about groundplanes lately, I still fear them for audio a bit. Maybe you can take away that fear.
You didn't had any noise or hum with this ground-plane? And if the answer is no, How did you get it so good?
With kind regards,
Bas
Dear Thomas,
I read his 4th and 5th edition. I am very aware. The reason why I point to the groundplane is, because many people who tried it in a power amplifier got groundloops and hum.
With kind regards,
Bas
Hi Sebastian
Glad to hear that you have read both version. I only have the old one, so you know more than me. I share you general view, that groundplan or should we say grounding in general can be very poroblematic.
I am no expert no this bt any means, but I think that something like starground and/or return currents in different parts of the amplifier (also the onces not on the PCB) can be quite tricky and not fully clear to a lot of people.
Have fun
Thomas
Glad to hear that you have read both version. I only have the old one, so you know more than me. I share you general view, that groundplan or should we say grounding in general can be very poroblematic.
I am no expert no this bt any means, but I think that something like starground and/or return currents in different parts of the amplifier (also the onces not on the PCB) can be quite tricky and not fully clear to a lot of people.
Have fun
Thomas
Dear Thomas,
I am personally very intrigued by grounding techniques. We simply have not enough time in life to become an expert in everything, and each subject alone you can spent a lifetime on. Grounding is one of those things.
One of the best books in my opinion according this subject is "Electromagnetic Compatibility Engineering" Amazon.com: Electromagnetic Compatibility Engineering (9780470189306): Henry Ott: Books
Chapter three tells a lot about grounding in a very understandable down to earth way (so even I can understand it
).The book mention basically four methods and the pros and the con's.
-Point to point star grounding
-serial star grounding
-groundplane
-combination of above
I was relieved to read that weather which technique you choose there isn't one "perfect" single solution. Star ground is a perfect cure for low frequency applications, since till around 100Khz. the current choose the way of the least resistance. With star-ground we can carefully route the currents and we can prevent hum issues. Above around 100Khz. current choose the way of the least inductance, and a star-ground doesn't provide a solution anymore.
However when a ground-plane is provided it can be a tradeoff between least inductance or least resistance, and it is much harder to control the loops.
Personally I believe a good implemented ground-plane provide superior performance. But myself I am still to afraid to apply it. I need to boost my knowledge about it till a next level. The fact you applied a ground-plane with good results (at least no ground-loop hums) gives me more hope. I am more then confident there would be a lot of interest in new boards or chip-amp developments from you.
Ps, I bought the above mentioned book as Ebook. If you want to "borrow" it from you can send me an email.
About D self's 5th edition. In comparison with the 4th edition, there is an extra article about power transistors with thermal compensation diodes inside the die. Well respected forum member Panson built great amplifiers with them, and has ton's of experiences with those devices. Another very interesting extra chapter was about low noise inout stages, where Mr Self smartly paralleled many NE5532 opamps (instrumentation stages) in order to obtain a very low noise input stage. Mr. Self is a great inspiration for me for a long time already, with very fresh insights.
Mention the 5532 and mostly the 5534. I was one of those audiophile snobs who never understood why any manufacture would use 5532/34's. Now I am getting older, and now I do more serious engineering and desire for very low noise amplification, I start to understand why those 5532/34 devices are still brilliant.
With kind regards,
Bas
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Dear Thomas,
I googled around trying to find any location where I could find the schematic of your Das Modul amplifier but came away empty handed. Can you please point me to the url of this site.
Also is the PCB for this project available with anyone? I wanted to build 8 of these power amps for my active speaker project (Orion+ by Linkwitz). The amplifiers recommended for this project are 60 W RMS per driver and I plan to use your design derated to just 60 W for the special requirements that I have
I stay in India where the ambient temperature where I live can get as hot as 44 C during summer and being conservative I am designing for 50 C as the ambient temperature.
The supply voltage is also not steady and can fluctuate around +/- 20% around the 220 V AC supply specs. hence to cater for these extremes, I would have to derate the 200 W amplifier considerably - and my calcualtion shows that derating to 60 W lives me with a lot of headroom - heat dissipation wise while keeping the amp THF+N figure less than 0.03%. From your perspective, am I being too conservative? and also where can I get the PCB for this design?
Regards,
Suvamoy
I googled around trying to find any location where I could find the schematic of your Das Modul amplifier but came away empty handed. Can you please point me to the url of this site.
Also is the PCB for this project available with anyone? I wanted to build 8 of these power amps for my active speaker project (Orion+ by Linkwitz). The amplifiers recommended for this project are 60 W RMS per driver and I plan to use your design derated to just 60 W for the special requirements that I have
I stay in India where the ambient temperature where I live can get as hot as 44 C during summer and being conservative I am designing for 50 C as the ambient temperature.
The supply voltage is also not steady and can fluctuate around +/- 20% around the 220 V AC supply specs. hence to cater for these extremes, I would have to derate the 200 W amplifier considerably - and my calcualtion shows that derating to 60 W lives me with a lot of headroom - heat dissipation wise while keeping the amp THF+N figure less than 0.03%. From your perspective, am I being too conservative? and also where can I get the PCB for this design?
Regards,
Suvamoy
Hi,
extra heat must be dissipated when your amplifier has to drive a low impedance speaker.
Bridging the chipamps makes everyone of the chips dissipate heat as if it were driving a load with half the impedance of your speaker. You will make heat dissipation more difficult by using bridging.
Are all the drivers in the Orion 8ohm?
Then use single chipamps to drive each speaker, no parallel loads.
If heat is as bad as you're suggesting, then reduce transformer (PSU) voltage down from 25Vac to 22Vac. This will reduce dissipation requirement and will also reduce the peak output power.
extra heat must be dissipated when your amplifier has to drive a low impedance speaker.
Bridging the chipamps makes everyone of the chips dissipate heat as if it were driving a load with half the impedance of your speaker. You will make heat dissipation more difficult by using bridging.
Are all the drivers in the Orion 8ohm?
Then use single chipamps to drive each speaker, no parallel loads.
If heat is as bad as you're suggesting, then reduce transformer (PSU) voltage down from 25Vac to 22Vac. This will reduce dissipation requirement and will also reduce the peak output power.
BPA-200 Das Modul derated to 60 W
I am planning to purchase the 8 ohms version, although the 4 ohms versions are also available. Also my earlier question on the schematic and the PCB. Are you still offering them for sale?
Would using the 4 ohms version reduce my power dissipation?
The heavy power derating would be needed considering the +/- 20% mains power fluctuation. During peak load in the summer (day time) supply voltage goes down as low as 180 VAC on the 220 VAC supply line and hence I ned to design for this voltage to get 60 W. If you consider that at the other extreme the voltage goes as high as 260 during light load conditions, then power dissipation would be very high for a system designed for 180 VAC. Hence the heavy derating of the 200 W system.
I am planning to purchase the 8 ohms version, although the 4 ohms versions are also available. Also my earlier question on the schematic and the PCB. Are you still offering them for sale?
Would using the 4 ohms version reduce my power dissipation?
The heavy power derating would be needed considering the +/- 20% mains power fluctuation. During peak load in the summer (day time) supply voltage goes down as low as 180 VAC on the 220 VAC supply line and hence I ned to design for this voltage to get 60 W. If you consider that at the other extreme the voltage goes as high as 260 during light load conditions, then power dissipation would be very high for a system designed for 180 VAC. Hence the heavy derating of the 200 W system.
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